Enhancing empirical SRP model for BDS-3 MEO satellites via semi-analytical accelerations analysis

Abstract

Currently, the significant challenge in achieving Precise Orbit Determination (POD) for the BeiDou Global Satellite Navigation System (BDS-3) lies in the Solar Radiation Pressure (SRP) model. The empirical CODE orbit model (ECOM) and its extended version, ECOM2, initially developed for the Global Positioning System (GPS) and the Russian Global Navigation Satellite System (GLONASS), are now widely employed not only for GPS and GLONASS but also for BDS and Galileo. However, applying ECOM and ECOM2 to BDS-3 reveals discrepancies, especially during eclipse seasons. To overcome this challenge, in this study, we proposed a refined ECOM with consideration of characteristics of SRP-induced accelerations acting on BDS-3 Medium Earth Orbit (MEO) satellites. First, we generate SRP-induced accelerations using the Adjustable Box-wing (ABW) model. Subsequently, we employ Fast Fourier Transform (FFT) to analyze the spectrum characteristics of these accelerations. The results indicate that the most prominent periodic terms are 1pr and 2pr terms in the D-direction and 1pr term in the B-direction. Parameter correlation analysis reveals that <i>D</i>_c,1 has a correlation coefficient nearly 1.0 with the parameter <i>B</i>₀. Consequently, we eliminate <i>D</i>_c,1 from the model. In eclipse seasons, the proposed model achieves an orbit Day Boundary Discontinuity (DBD) accuracy of about 30 mm. Compared to other ECOMs, it demonstrates an improvement ranging from 8 % to 44 %. Additionally, the orbit prediction precision reaches approximately 60 mm, surpassing other ECOMs by 9 %–43 %. The STD of SLR residuals for CAST satellites during eclipse season also shows improvements of 8 %–25 % compared to other ECOMs. These results affirm the proposed model is well-suited for BDS-3 MEO satellites POD, especially during eclipse seasons.